In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations and/or user equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a Base Station (BS), e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or by an antenna at an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole wireless communication network is also broadcasted in the cell. One base station may have one or more cells. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations in downlink (DL) to the user equipments and uplink (UL) from the user equipments.
A Universal Mobile Telecommunications System (UMTS) is a third generation wireless communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations nodes, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio base stations connected directly to one or more core networks, i.e. they are not connected to RNCs.
A machine-to-machine (M2M) communication, aka machine type communication (MTC), is used for establishing communication between machines and between machines and humans. The M2M communication may comprise exchange of data, signaling, measurement data, configuration information etc. The size of a M2M device may vary from e.g. that of a wallet to that of a base station. The M2M devices are quite often used for applications like sensing environmental conditions e.g. temperature reading, metering or measurement e.g. electricity usage etc., fault finding or error detection etc. In these applications the M2M devices are active very seldom but over a consecutive duration depending upon the type of service e.g. about 200 ms once every 2 seconds, about 500 ms every 60 minutes etc. The M2M devices may also do measurement on other frequencies or other Radio access Technologies (RAT).
An M2M device may be a Low complexity UE, thus being an M2M device of low cost and low complexity. A low complexity UE that envisages for M2M operation may implement one or more low cost features like, smaller downlink and uplink maximum transport block size, e.g. 1000 bits, and/or reduced downlink channel bandwidth of 1.4 MHz for data channel, e.g. Physical Downlink Shared Channel (PDSCH). A low complexity UE may also comprise a Half-Duplex communication e.g. Half Duplex-Frequency Division Duplex (HD-FDD) and one or more of the following additional features: a single receiver at the UE, smaller downlink and/or uplink maximum transport block size e.g. 1000 bits, and a reduced downlink channel bandwidth of 1.4 MHz for data channel. The low complexity UE may also be termed as low cost UE.
The path loss between the M2M device and the base station can be very large in some scenarios such as when the M2M device is used as a sensor or metering device located in a remote location such as in the basement of a building. In such scenarios a reception of signal from base station is very challenging. For example the path loss can be worse than 20 dB compared to normal operation. In order to cope with such challenges the coverage in uplink and/or in downlink has to be substantially enhanced. This is realized by employing one or plurality of advanced techniques in the M2M device and/or in the base station for enhancing the coverage. Some non-limiting examples of such advanced techniques may be: transmit power boosting; repetition of transmitted signal; applying additional redundancy to the transmitted signal; use of advanced/enhanced receiver etc. In general when employing such coverage enhancing techniques the M2M communication is regarded to be operating in a coverage enhancing mode. A low complexity UE e.g. a UE with one single receiver (Rx) may also be capable of supporting enhanced coverage mode of operation.
Discontinuous Reception (DRX) Cycle Operation
In LTE a DRX cycle is used to enable the UE to save its battery. The DRX cycle is used in Radio Resource Control (RRC) idle state but it can also be used in RRC connected state. Examples of lengths of DRX cycles currently used in RRC idle state are 320 ms, 640 ms, 1.28 s and 2.56 s. Examples of lengths of DRX cycles currently used in RRC connected state may range from 2 ms to 2.56 s.
The DRX cycle is configured by a network node such as a radio access node or control network node and is characterized by the following parameters:                On duration: During the on duration of the DRX cycle, a timer called ‘on-Duration-Timer’, which is configured by the network node, is running. This timer specifies a number of consecutive control channel subframes, e.g. Physical Downlink Control Channel (PDCCH), enhanced Physical Downlink Control Channel (ePDCCH) subframe(s), at the beginning of a DRX Cycle. It is also interchangeably called as DRX ON period. More specifically it is the duration in downlink subframes that the UE after waking up from DRX to receive control channel, e.g. PDCCH, ePDCCH. If the UE successfully decodes the control channel, e.g. PDCCH, ePDCCH, during the ON duration then the UE starts a drx-inactivity timer and stays awake until its expiry. When the onDurationTimer is running the UE is considered to be in a DRX state of the DRX cycle.        drx-inactivity timer: The drx-inactivity timer specifies the number of consecutive control channel, e.g. PDCCH, ePDCCH, subframe(s) after the subframe in which a control channel, e.g. PDCCH, indicates an initial UL or DL user data transmission for this Medium Access Control (MAC) entity. It is also configured by the network node. When the drx-inactivity timer is running the UE is considered to be in a non-DRX state i.e. no DRX is used.        Active time: This time is the duration during which the UE monitors the control channel, e.g. PDCCH, ePDCCH. In other words this is the total duration during which the UE is awake. This includes the “on-duration” of the DRX cycle, the time during which the UE is performing continuous reception while the drx-inactivity timer has not expired and the time the UE is performing continuous reception while waiting for a DL retransmission after one Hybrid Automatic Repeat Request Round-Trip Time (HARQ RTT). The minimum active time is equal to the length of an on duration, and the maximum active time is undefined (infinite).        
The DRX ON and DRX OFF durations of the DRX cycle are shown in FIG. 1. The DRX operation with more detailed parameters in LTE is illustrated in FIG. 2 showing where the UE or wireless device shall monitor the PDCCH i.e. during the on Duration period and followed by the opportunity for DRX. Using a wireless device for e.g. M2M communication with present DRX setting is a rather rigid solution and may limit the performance of the wireless communication network.